Inflammatory bowel disease (IBD) refers to a group of gastrointestinal disorders characterized by chronic, relapsing inflammatory disorders of the gastrointestinal tract. Crohn's disease and ulcerative colitis are the two main subtypes of IBD.
The etiology of IBD is unclear. IBD appears as multifactorial disease, with genetic and environmental factors probably cooperating in their development.
Patients typically suffer from frequent and chronically relapsing flares, resulting in diarrhea, abdominal pain, rectal bleeding and malnutrition. Crohn's disease can be distinguished from ulcerative colitis in that the inflammation associated with Crohn's disease is transmural and often discontinuous. By contrast, the inflammatory changes of ulcerative colitis typically involve only the superficial mucosal and submucosal layers of the intestinal wall. Crohn's disease most commonly involves the ileum and colon but can affect any region of the gut; ulcerative colitis always involves the rectum, and inflammation may extend as far as the caecum in a continuous pattern. Patients with IBD often have various extra-intestinal symptoms such as arthalgias, and are more likely to have other chronic inflammatory diseases, particularly primary sclerosing cholangitis, ankylosing spondylitis and psoriasis. Etiology, genetics and pathogenesis of IBD is described by Hugot (1999) and Cho (2008).
Since the etiology of both diseases is undetermined the causal therapy does not exist. The most commonly used conventional therapies are anti-inflammatory medicaments such as corticosteroids, salicilates, and immunosuppressives such as cyclosporine, mercaptopurine and azathioprine. Recently, biologic therapies have received a great amount of attention.
The mucosal immune system is the central effector of intestinal inflammation and injury, with cytokines playing a central role in modulating inflammation. Cytokines may, therefore, be a logical target for IBD therapy using specific cytokine inhibitors. In this context compounds described by Schwartz M (2008) blocking the effect of tumor necrosis factor α (TNFα) or its receptor are of interest.
TNFα is a cytokine produced by numerous cell types, including monocytes and macrophages, and was originally identified on the base its ability to induce the necrosis of certain mouse tumors as described by Old (1985). TNFα has been implicated in the pathophysiology of a variety of other human diseases and disorders, including sepsis, infections, autoimmune diseases, transplant rejection and graft-versus-host disease. TNFα promotes the inflammatory response, which, in turn, causes many of the clinical problems associated with autoimmune disorders such as rheumatoid arthritis, ankylosing spondylitis, Crohn's disease, psoriasis and refractory asthma. These disorders are sometimes treated by using a TNFα inhibitor or by counteracting TNFα activity.
In particular, monoclonal antibodies against TNFα are routinely used in parenteral therapy of IBD as described by Sandborn (1999). Commercially available are infliximab, adalimumab and certolizumab pegol. Since antibodies are administered mainly by subcutaneous injection, serious unwanted effects emerge such as headache, abscess, upper respiratory tract infection and fatigue.
De Silva (1992) reported on abundant presence of TNFα in the stool of IBD patients. Local delivery on the place of inflammation could solve unwanted effects associated with systemic delivery. This was achieved by Worledge (2000), with successful treatment of experimental colitis in rats by orally administering avian IgY anti TNFα antibodies with the capability of deactivating/removing TNFα.
Antibodies and antibody related derivatives against TNFα are not always the optimal choice. The high cost of production of these immunoglobulin preparations prohibits their large-scale application. Antibodies, like other protein molecules, are not stable in the gastrointestinal tract.
The use of genetically engineered bacteria that produce and deliver compounds that block the activity of TNFα could provide a solution. In this respect, lactic acid bacteria, which are normal commensals of the gut and other mucosal surfaces of human and animals and generally regarded as safe, represent ideal candidates.
WO2007/025977 discloses delivery of secreted antibodies against TNFα, and of fragments of such antibodies (so-called nanobodies), to the intestine for the treatment of enterocolitis using genetically engineered microorganisms such as lactic acid bacteria. The secreted antibodies of WO2007/025977 do not include a surface attachment domain, and are thus not attached to the cell's surface and more prone to chemical and biological degradation in the gut.
WO97/14806 discloses a delivery system of biologically active compounds in the intestine, wherein non-invasive bacteria such as lactic acid bacteria are used to deliver biological active polypeptides to the gut. WO00/23471 discloses recombinant lactic acid bacteria that can be used to deliver IL-10 and soluble TNF receptor via oral route to the ileum to treat IBD. No attachment of the polypeptides to the surface of the microorganism is disclosed. Hence, the polypeptides are subject to rapid degradation. WO97/14806 uses the Usp45 secretion domain to ensure efficient secretion of the proteins.
EP1477802 discloses vaccines against infection with Streptococcus pneunoniae. The vaccine comprises the antigenic part of pneumococcal proteins (PpmA, SlrA), which are fused with a cell wall anchoring domain derived from the AcmA protein. The pneumococcal proteins of EP 1477802, however, do not comprise a TNFα binding domain, hence do not exhibit the therapeutic effects of the present microorganisms.
Hence it is known to produce peptides by lactic acid bacteria and secrete them into the gastrointestinal tract. Such peptides then generally undergo fast degradation.